The invention relates to a disc brake comprising a brake disc and two brake shoes, which are pressable against both sides of the brake disc and in relation to a peripheral force generated upon application of the brake shoes against the brake disc are supported against a vehicle-fixed carrier, and comprising at least one device for measuring and/or converting the peripheral force, which device is disposed in a force transmission chain between at least one of the brake shoes and the carrier.
Modern brake systems, for control and feedback control purposes, require an exact measurement of the forces occurring during a braking operation. Usually, these forces are subdivided into transverse forces (also known as normal forces or clamping forces) and peripheral forces (also known as frictional forces). The component of force introduced by a brake shoe into the brake disc at right angles to the plane of the brake disc is described as a transverse force. By peripheral force, on the other hand, is meant the component of force, which on account of the brake friction between a friction lining of the brake shoe and the brake disc acts in peripheral direction of the brake disc upon the brake shoe. By multiplying the peripheral force by the distance of the application point of the peripheral force from the axis of rotation of the wheels, the braking torque may be determined.
Many applications require an exact knowledge of the actual magnitude of the braking torque and hence also an exact knowledge of the peripheral force. For example, the braking torque may be used to form a precise closed-loop control circuit for electrohydraulic and electromotive brake systems.
In the case of the disc brake known from DE-GM 90 10 026, and corresponding U.S. Pat. No. 5,279,394, both of which are incorporated by reference herein, measurement of the peripheral force is effected by means of a force sensor, which is disposed on or in a guide pin. This guide pin is firmly connected to the initially mentioned, vehicle-fixed carrier and engages into a slide groove. The slide groove is formed on a structural part connected rigidly to one of the brake shoes and is displaceable in relation to the guide pin.
A further disc brake, which for measuring the peripheral force comprises a force sensor disposed in a force transmission chain between at least one of the brake shoes and a vehicle-fixed carrier, is known from DE 196 39 686, and corresponding U.S. Pat. No. 6,059,379, both of which are incorporated by reference herein. The force sensor is disposed on a fastening screw, by means of which a caliper of the disc brake is connected to the vehicle-fixed carrier.
It has been found that measurement of the peripheral force in the disc brakes known from prior art is prone to error because of various influences. These errors make it difficult to achieve precise control or feedback control of brake systems.
The underlying object of the invention is to indicate a disc brake, which allows a more exact determination of the peripheral forces that occur during a braking operation.